JPH09170614A - Method and equipment for reducing rotational resistance of bolt - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method and an apparatus for releasing a bolt without sticking of the bolt stacked in a nuclear reactor vessel in order to prevent the bolt from removing by using a drill. SOLUTION: A nuclear reactor chamber comprises a blind hole 90, which receives a bolt 130 having a center path 170. To this path a pulser pump is connected for supplying pulsating liquid to the path, namely the blind hole. When the liquid exits the path, liquid pushes the bottom of the blind hole to apply upward liquid force to the bolt end to lift upwardly the bolt. A controller is connected to the pulser pump for controllably operates the pulser pump. Since the hydraulic pressure of pulsating fluid lifts up the bolt, the fluid moves into the gap between the bolt and the thread in the blind hole to remove or peel off dust therebetween and rinse dust upwardly between the bolt and the blind hole to transfer to the suction pump communicating to the blind hole.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION This invention relates generally to methods and apparatus used in the maintenance of nuclear reactor pressure vessels, and in particular to
A method and apparatus for loosening stuck bolts in a reactor pressure vessel.

[0002]

BACKGROUND OF THE INVENTION A typical nuclear reactor pressure vessel includes a body having an open top end and a flange surrounding the top end. An airtight closed head closes the barrel and a flange surrounds the closed head. The sealing head flange and the body flange are coaxially aligned and are joined together by a plurality of spaced vertically disposed bolts. Each bolt extends through a smooth hole formed through the sealed head flange and enters a blind hole with a female thread formed in the body flange. A threaded nut is screwed onto each bolt and tightened against the top of the sealing head flange to secure the sealing head to the barrel. In order to perform maintenance on the inside of the reactor, unscrew these nuts from the bolts, remove the bolts from the blind holes with internal threads formed in the body flange, and then attach to the sealed head flange. Remove the sealing head by sliding the bolt upward through a smooth hole. After performing maintenance on the inside of the reactor, add a lubricant (for example, an alcohol-containing or oil-based liquid lubricant) to the threaded part of the blind hole and the threaded part of the bolt, and reattach the sealed head to the body. Make it easier to screw the bolt into the blind hole when doing.

However, according to the knowledge of the inventor of the present invention, typically, during the operation of the reactor for 18 months, the above-mentioned lubricant is dried and hardened due to the temperature rise of the wall of the reactor vessel. Due to the relatively high temperature of the reactor vessel, the alcohol in the alcohol-containing liquid lubricant evaporates or the oil-based lubricant carbonizes, and the lubricant tends to dry and harden. During this period, dry concrete deposits or dust remain. Furthermore, if the threads of the bolt were damaged (eg, pitted) during a previous maintenance operation, the presence of dust would attach to the damaged portion of the bolt threads and then during future maintenance inside the reactor. Scratch or scratch the surface of the thread when attempting to loosen and remove the bolt from the blind hole (eg, scratch or tear).
Such a scratched thread causes the bolt to stack, i.e., to become immobile, thus providing resistance in loosening the bolt from the threaded blind hole. That is, hardened debris and stuck bolts make it increasingly difficult, and often impossible, to unscrew them by simply rotating the stacked bolts in the reactor vessel with a normal amount of torque.

One prior art solution to the problem of stacked bolts in a reactor vessel is to simply rotate the bolts with a very large force to force the bolts to free. However, the present inventor has found that this "force-pulling method" of removing stuck bolts further scratches the bolt threads due to the continued presence of hardened debris between the bolt and blind thread threads. , I found that I might pit. Moreover, to the inventor's knowledge, the only practical way to remove a bolt from a blind hole is often to use a drill to remove the bolt, which is time consuming and This is an expensive method. Drilling out the stacked bolts costs 42 million yen ($ 300,000) per bolt, and there is a delay in bringing the reactor back into operation.

Accordingly, a problem in the prior art is to provide a method and apparatus for loosening the stacked bolts of a reactor vessel without causing further galling and avoiding the use of drilling the bolts. There is a point that it does not provide.

[0006]

SUMMARY OF THE INVENTION This specification discloses a method and apparatus for loosening stacked bolts in a reactor pressure vessel. The reactor pressure vessel has a threaded blind hole that receives an upright bolt having a passageway centrally disposed longitudinally therethrough. A pulsar pump communicates with this passage to supply pulsating liquid to the passage and thus to the blind hole. As the fluid exits the passage, it presses against the bottom of the blind hole, exerting an upward hydraulic force against the end of the bolt, lifting the bolt upwards. A controller is connected to the pulsar pump to controllably operate the pulsar pump. Since the hydraulic force of the pulsating fluid lifts the bolt, the fluid moves between the bolt and the threaded portion of the blind hole to separate or remove dust from between the two,
Flush the dust upwards between the bolt and the blind hole and send it to the suction pump that communicates with the blind hole. The suction pump sucks the liquid containing dust from the blind hole. The drag reduction device of the present invention includes a rotating tool connected to the bolt to rotate the bolt as the liquid is pulsed to facilitate removal of dirt from the threads. The removal of dust allows the bolt to rotate with reduced resistance to rotation and with a normal amount of applied torque.

The invention, in its broadest form, relates to a reactor vessel having a threaded hole therein and a bolt threadably engaged with the hole and resisting rotation. A device for reducing the resistance of the bolt to rotation, the bolt vibrating means associated with the bolt for vibrating the bolt, and connected to the bolt vibrating means for supporting the bolt vibrating means. And a rotation resistance reducing device for the bolt, which comprises:

The invention, in its broadest form, also comprises:
Used in connection with a reactor vessel having a threaded hole therein and having a bolt threadably engaged with the hole and resisting rotation to reduce the resistance of the bolt to rotation. A method for reducing the rotational resistance of a bolt, the method including vibrating the bolt.

It is an object of the present invention to loosen the stacked bolts of a reactor pressure vessel in such a way that it is not necessary to remove the bolts in a "brute force" manner, and yet the stacked bolts need not be removed using a drill. Method and apparatus.

A feature of the present invention is the provision of fluid pulsation supply means in communication with the blind holes for supplying the pulsating fluid into the blind holes to lift the stacked bolts.

Another feature of the invention comprises bolt rotation means associated with the fluid pulsation supply means for rotating the bolt as it is lifted so that the stacked bolt is released from its stacked condition. It is that.

An advantage of the present invention is that the stacked bolts are removed without the use of a "brute force" method so that the stacked bolts are not galled further.

Yet another advantage of the present invention is that the use of the present invention avoids the added cost and work delay associated with drilling stacked bolts.

With reference to the following detailed description in connection with the accompanying drawings, which show and explain embodiments of the invention, the above-mentioned objects, features and advantages of the invention as well as other objects,
Features and advantages will be apparent to those of ordinary skill in the art.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to FIGS. 1 and 2, there is seen a reactor pressure vessel generally designated 10 (hereinafter also referred to as a reactor vessel). The pressure vessel 10 is located within a reactor cavity 20 defined by a containment structure 30. The containment structure 30 includes an annular ledge 40 surrounding the cavity 20 to provide a workbench for equipment and service personnel. The body 50 of the pressure vessel 10 has an open top end 60 to allow access to the internals 70 located therein. Pressure vessel body 50
The flange 80 is located around the open top end 60 of the body 50, and is formed with a plurality of threaded blind holes 90 spaced apart. Each blind hole 90 terminates in a recess 95.

Still referring to FIGS. 1 and 2, an airtight closure head 100 closes the open top end 60. The sealing head flange 110 surrounds the perimeter of the sealing head 100 and has a plurality of spaced apart smooth through holes 120 that are coaxially aligned with each blind hole 90. ing. Extending through each through hole 120 and threaded into the blind hole 90 is an elongated bolt 130. Each bolt 130
Has an externally threaded tip 140 and an externally threaded proximal end 150. The threaded portion of the tip portion 140 is screwed into the threaded portion of the blind hole 90. Since the threaded portion of the tip portion 140 and the threaded portion of the blind hole 90 are screwed together, the tip portion 14
0 and the flange 80 of the body of the pressure vessel, a gap 152
Is defined (see FIG. 9), and this gap 152 is a recess 95.
(See FIG. 9). Further, as shown in FIGS. 1 and 2, the tip 140 has a downwardly facing end surface 155 located adjacent to or blocking the recess 95. Threaded into the proximal end 150 of each bolt 130 is a nut 160 that is internally threaded so that the bolt 130 can be stopped.
00 is snugly engaged to the top surface of the sealing head flange 110 to attach the 00 to the open top end 60 of the barrel 50. The nut 160 has at least two grooves 165 on its top surface on the end surface that receives the nut rotating tool (not shown). As can be seen from the above description, the term "tip" is defined as meaning the end of the cavity 20 closer to the floor, and the term "proximal" is defined from the floor of the cavity 20. It is defined here as meaning the more distant end.

Referring to FIGS. 2, 3 and 4, elongated bolt 130 is longitudinally pre-pierced to receive an elongated gauge (not shown) used to measure the tension of bolt 130. Having a passage 170. In this regard, a bolt tensioning device (not shown), which does not form part of the present invention, is used to tension the bolt 130 before the nut 160 stops the bolt 130. Due to the tension of the bolt 130, the closed head 10
0 to the pressure vessel body 50 to secure the nut 160
Can be tightly engaged with the top surface of the sealing head flange 110. The elongated gauge described above is inserted into the passage 170 to measure the tension of the bolt 130. Specifically, the gauge is inserted into the passage 170 and the pre- and post-tension distance between the top of the bolt and an elongated rod (not shown) also located within the passage 170 is measured to determine the amount of tension in the bolt 130. Ask for. As will be described in more detail below, it is advantageous to use the presence of this passage 170 in helping to loosen the stuck or stuck bolt 130.

With reference to FIGS. 5 and 6, prior to use of the present invention, the tip 140 of the bolt 130 is shown threaded into the blind hole 90. On the outside of the bolt 130, there are a plurality of outwardly projecting burr-like portions or projections 180 (only one is shown), and the projections 180 penetrate the surface of the threaded portion of the blind hole 90, When attempting to rotate 130, the bolt 130 will gnaw or stick.

Returning to FIG. 1, the bolt 13 is stuck.
The device which is the subject of the invention for reducing the zero (rotational drag reduction device) is indicated generally by the reference numeral 190. The device 190 comprises support means such as an adjustable support platform 200 for the reasons disclosed herein.
The support platform 200 includes a plurality of adjustable legs 210 that ride on the ledge 40, which raises or lowers the height of the support platform 200 to facilitate working with the bolts 130. You can Further, the device 190 includes bolt vibrating means, generally indicated at 220, associated with the bolt 130 for vibrating the bolt 130 so that the stuck bolt 130 can be loosened to remove the bolt 130. It can be rotated substantially without resistance during or after vibration. As will be described in detail, the vibrating means 220 may be hydraulic vibrating means. Specifically, the vibrating means 220 is
A fluid pulsation supply means, such as a fluid supply pulsar pump 230, supported by the support platform 200 is preferably provided. The pulsar pump 230 supplies a pulsating fluid (eg, demineralized water or oil) into the passage 170 and into the recess 95 from which it oscillates (eg, repeatedly translates or raises upwards).
The pulsar pump 230 preferably pulsates the fluid at a frequency of about 1-10 pulses per second. The fluid pulsation supply means further includes a fluid supply tank 23 connected to the pulsar pump 230 for supplying fluid to the pulsar pump 230.
5 is provided. Further, the fluid pulsation supply means supplies the pulsated fluid into the passage 170 so as to supply the pulser pump 23.
Flexible first conduit 240 extending from 0 into the passage 170
It has. The pulsating fluid flows downward through the passage 170 and enters the recess 95, filling the passage 170 and the recess 95.

As best shown in FIGS. 1, 7 and 8, the device 190 further comprises a liquid suction means in communication with the blind hole 90 for generating a suction force therein. This liquid suction means surrounds the mouth portion of the blind hole 90 and the body portion 6
It comprises a segmented torus-shaped liquid collection tank 250 that rides on top of the zero. The liquid collecting tank 250 is
It has a chamber 260 inside for collecting fluid aspirated from the blind hole 90. The liquid collecting tank 250 must include a plurality of segments 270.
70 are sealably coupled or locked to each other by locking joints 280 that are each interposed between adjacent segments. The segment structure of the liquid collection tank 250 allows for the placement and removal of the liquid collection tank with the bolt closure head 100 held in place. The liquid collecting tank 250 may further have a plurality of suction ports 290 projecting downward toward the mouth of the blind hole 90 in order to suck the fluid discharged from the mouth of the blind hole 90 therein.
Each suction port 290 includes a one-way flap valve (not shown) that can be operated to prevent liquid from flowing through the suction port 290 and once it enters the chamber 260, the liquid can flow out of the chamber 260. be able to. Flexible second conduit 300
Has one end communicating with the chamber 260 and the other end connected to a suction pump 310 that may be attached to the support platform 200. The fluid once drawn into the liquid collection tank 250 may be disposed of in a manner conventionally reserved for the disposal of liquid radioactive waste, if desired.

Referring to FIGS. 9 and 10, the pulsar pump 230 preferably supplies a pulsating fluid at a frequency of about 1 to 10 pulses per second downwardly into the recess 95 via the passage 170, and the passage 170. And fill the recess 95. As the fluid is pulsated by the pulsar pump 230, the fluid in the recess 95 impinges on the end face 155 of the immobile bolt 130, causing an upwardly directed hydraulic force acting on the end face 155. Occur. As the hydraulic force acts on the end surface 155 of the bolt 130, the upward force of the fluid lifts the bolt 130 within the blind hole 90 by a predetermined intermediate distance "L". In this way, the bolt 13
0 weight is lifted from the threaded surface of the blind hole 90,
It helps release the bolt 130 from a stuck state.

As best shown in FIGS. 10 and 11, dust or debris 330 is between the bolt and the threaded portion of the blind hole. This dust 330 has a threaded portion of the blind hole 90 and / or
Or, it is a hardened dry lubricant residue that adheres to the surface of the threaded portion of the bolt 130. Such hardened concrete-like debris may interfere with, or even interfere with, the rotation of the bolt 130 in the blind hole 90. In that sense, the bolts 130 get stuck in the blind hole 90, i.e. stuck. However, the pulsating fluid flowing between the threaded portion of the bolt 130 and the threaded portion of the blind hole 90 causes dust 330 to release the bolt 130 from its stacked condition.
Has a sufficient liquid force to loosen the corroded portion 180. In this regard, the fluid in the recess 95 travels through the previously described gap 152 and then in a spiral step defined between the threads of the bolt 130 and the blind hole 90. It moves through the intervening space 320. The fluid flow paths are indicated schematically by the arrows in FIG. Due to the continuous pulsation of the fluid, the fluid is forced upwardly through the entire length of the space 320 and aspirated through the suction port 290 and blinded into the chamber 260 defined by the liquid collection tank 250. Exit from 90 mouth. The fluid can then be disposed of in the manner routinely used in the art.

As shown in FIG. 12, the hydraulic force exerted against the end surface 155 during the pulsation of the fluid further translates the bolt 130 upwards up to a predetermined distance L'if desired.
Between pulses, the bolt 130 preferably attempts to fall by gravity to the initial position shown in FIG. 5, but the fluid again pulsates to lift the bolt 130.

Returning to FIGS. 1, 2 and 3, the device 190
Further comprises rotating means such as a bolt rotating tool generally indicated at 340. The bolt rotation tool 340 rotates the bolt 130 when the pulsar pump 230 pulsates the fluid, so that the proximal end portion 150 of the bolt 130 is rotated.
It is detachably connected to. The bolt 130 that is rotating when the fluid is pulsed is the bolt that is more free from its stack. The bolt rotation tool 340 includes a support member 350 slidably connected to the base end portion 150 of the bolt 130, and the support member 3
Included is a motor 360 attached to 50. The bolt rotation tool 340 also includes drive means, such as a continuous drive belt 370, which encloses a cap member 380 connected to the proximal end 150 of the bolt 130. The drive belt 370 is connected to a motor 360 for driving the drive belt, thus rotating the cap member 380. The bolt 130 rotates as the cap member 380 rotates. A typical rotary tool for this purpose is disclosed in US Pat. No. 4,223,575. The device 190 also includes bolts 13
Controlling means, such as a controller 390, may be included in the pulsar pump 230 to controllably operate the pulsar pump 230 such that a pulse of the desired frequency is obtained when the zero rotates. Controller 39
0 may include a computer for automatically and controllably operating the pulsar pump 230.

By way of example only, and not by way of limitation, the bolt 130 weighs approximately 363.6 Kg.
(800 lbs), approximately 152.4 cm (60 inches) in length, and 15.2-17.8 cm (6-7 inches) in diameter. Therefore, it is difficult or even impossible to use the "brute force" method of loosening a stuck bolt 130 due to the overall weight and size of the bolt 130. However, the pulsar pump 230 exerts about 1500 pounds of force against the end face 155 during each pulsation. This force is sufficient to lift the relatively heavy bolt 130, which can be rotated as described above.

As will be apparent from the foregoing description, the advantage of the present invention is that it avoids the use of a brute force method of removing stuck reactor vessel bolts, which may result in further galling of the bolt threads. Alternatively, it is possible to prevent scratching.

Another advantage of the present invention is that it avoids the increased costs and delays associated with drilling out stuck reactor vessel bolts.

While the present invention has been disclosed and described with respect to its preferred embodiments, it is not intended to be limited to the details disclosed and described, but to depart from the spirit of the invention,
It should be understood that various modifications can be made without departing from the range of equivalence. For example, the bolt can be sufficiently loosened by hydraulically lifting the bolt without rotating the bolt.

Accordingly, a method and apparatus has been provided for loosening stuck bolts in a reactor pressure vessel.

[Brief description of the drawings]

FIG. 1 is a typical example having a lower barrel and a closed head that is non-rotatably secured in the barrel by threaded bolts that are stacked in the threaded hole formed in the barrel. FIG. 3 shows a partial vertical cross-section of a pressure vessel of another pressurized water nuclear reactor (PWR) and shows an apparatus of the present invention positioned nearby to loosen stacked bolts by supplying pulsating fluid to the holes.

FIG. 2 shows a partial vertical cross section of stacked bolts in a hole.

FIG. 3 shows a partial vertical section of a rotary tool mounted on a bolt for rotating it.

4 is a cross-sectional view taken along line 4-4 of FIG.

FIG. 5 is a partial vertical cross-sectional view of a bolt threadably engaged with a threaded portion of a hole before starting a bolt loosening step.

FIG. 6 is a partial vertical cross-sectional view of a bolt having a corroded portion caused by prior galling of the bolt within the hole.

FIG. 7 is a vertical cross-sectional view of a fluid collection tank for aspirating and storing fluid from a hole when a bolt is loosened.

8 is a sectional view taken along line 8-8 of FIG.

FIG. 9 shows a partial vertical section of the bolt lifted by a predetermined intermediate distance in the hole by a pulse of fluid acting on the lower end of the bolt.

FIG. 10 shows a partial vertical cross section of the bolt lifted in the hole by said predetermined intermediate distance, which also shows the dust and corrosion present between the hole and the threaded part of the bolt.

FIG. 11: Bolt lifted by a predetermined maximum distance in a hole, showing dust removed from thread of bolt due to pulsating action of fluid, and showing that corroded portion decreased due to peening action to become dust It is a partial vertical sectional view of a screw part.

FIG. 12 is a partial vertical cross-sectional view showing a bolt screw portion lifted by a predetermined maximum distance in a hole by a hydraulic force of a fluid acting on a lower end portion of the bolt.

[Explanation of symbols]

10 ... Reactor pressure vessel (reactor vessel), 90 ... Hole (blind hole), 95 ... Recess, 120 ... Hole, 130 ... Bolt, 14
0 ... Bolt tip, 170 ... Passage, 190 ... Device (rotational resistance reducing device), 200 ... Support platform (supporting means), 220 ... Bolt vibrating means, 230 ... Pulsar pump (liquid pulsation supplying means), 235 ... Liquid Supply tank, 240 ... First conduit, 250 ... Liquid collecting tank, 26
0 ... Chamber, 300 ... Second conduit, 310 ... Suction pump, 33
0 ... dust, 340 ... bolt rotating tool, 390 ... controller.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hermann Schenberger, Federal Republic of Germany, 4670 Lune, Industrie Strasse 1

Claims (5)

[Claims] 1. A bolt for rotation, used in connection with a reactor vessel having a threaded hole therein and having a bolt threadably engaged with the hole and resisting rotation. (A) a bolt vibrating means linked to the bolt for vibrating the bolt, and (b) connected to the bolt vibrating means for supporting the bolt vibrating means. A rotation resistance reducing device for a bolt, comprising: a supporting means. 2. A bolt for rotation, used in connection with a reactor vessel having a threaded hole therein and having a bolt threadably engaged with the hole and resisting rotation. (A) in cooperation with the bolt for vibrating the bolt to reduce the resistance to rotation and rotate the bolt after the bolt is vibrated. And a liquid pulsation supply means for supplying a pulsating liquid into the hole, and (b) the liquid pulsation supply means for supporting the liquid pulsation supply means. A device for reducing the rotational resistance of a bolt, comprising a supporting means connected thereto. 3. A blind hole having a first threaded portion and vertically oriented with a recess defining a recess, the blind hole being threadably engageable with the first threaded portion. Receives an upright elongate bolt having a second threaded portion engaging with and having a tip disposed proximate the recess, the bolt having a predetermined weight and communicating with the recess. A device for reducing the resistance of the bolt to rotation, the device being used in connection with a reactor vessel having a centrally arranged passage therethrough longitudinally, comprising: A liquid pulsation supply means communicating with the passage for supplying into the passage and the recess, the liquid pulsation supply means including a liquid supply pulsar pump capable of pulsating the liquid; and (b) the liquid supply pulsar pump. To support the liquid Liquid suction means comprising a support platform connected to a pulsar pump, (c) a liquid suction means communicating with said blind hole for sucking liquid from said blind hole, (i) for collecting liquid sucked from said blind hole An annular liquid collecting tank which defines a chamber communicating with the blind hole therein, and (ii) a suction force is generated in the chamber so that the liquid is sucked from the blind hole and enters the chamber. A liquid suction means including a suction pump communicating with the chamber, and (d) a liquid supply tank connected to the liquid supply pulsar pump for supplying the liquid to the liquid supply pulsar pump. And (e) a controller connected to the liquid supply pulser pump for controllably operating the liquid supply pulser pump, the controller including the controller. Pulsating the liquid in the passage and the recess when the pump is controllably operated, and applying an intermittent hydraulic force to the tip of the bolt when the liquid in the recess is pulsated. When the hydraulic force acts on the tip of the bolt, the bolt is lifted in the blind hole by a predetermined distance, and when the bolt is lifted, the weight of the bolt applied to all the first screw parts is reduced. The liquid is moved between the first screw part and the second screw part, and when the liquid moves between the first screw part and the second screw part, the first screw part and Loosening the dust between the second screw portions, the dust loosens and the first dust
A rotation resistance reducing device for a bolt, which is capable of rotating the bolt with a reduced resistance to rotation when the weight of the bolt applied to the thread portion of the bolt decreases. 4. A bolt for rotation, used in connection with a reactor vessel having a threaded hole therein and having a bolt threadably engaged with the hole and resisting rotation. A method for reducing the rotational resistance of a bolt, comprising the step of vibrating the bolt. 5. A blind hole having a first threaded portion and vertically oriented with a recess defining a recess, the blind hole being threadably engageable with the first threaded portion. Receiving an upright elongate bolt having a second threaded portion engaging with and having a tip located proximate the recess, the first threaded portion and the second threaded portion having Having a dust between which resists rotation of the bolt in the blind hole,
The bolt is used in connection with a reactor vessel having a predetermined weight and having a centrally located passage therethrough longitudinally so as to communicate with the recess, to increase the resistance of the bolt to rotation. A method for reducing the weight of the second thread of the bolt from the first thread of a blind hole by supplying pulsating liquid into the passage and into the recess. A liquid that exerts an upward hydraulic force on the tip of the bolt when the liquid is pulsated, lifts the bolt, and when the bolt is lifted, the first screw portion and the second screw A liquid that moves between the parts loosens the dust and allows the bolt to rotate with reduced resistance to rotation as the dust loosens and the bolt is lifted. Reduction method.